1. If you use the same demat account, then you will only we able to buy shares through Zerodha. When you intend to sell, you will have to use the services & pay charges to ICICI since the shares would be in your ICICI demat account. In order to avoid paying such higher charges, we would advice you to open a trading & demat account at Zerodha.
2. You can download our account opening forms from here: https://zerodha.com/downloads. Else just leave your information here: https://zerodha.com/open-account and one of our Sales Managers will get in touch with you and help you open your account.
3. Since it’s a delivery trade, you don’t pay any brokerage. Yes, you heard it right! 0 brokerage for all delivery trades. There are a few statutory charges like Exchange fee, STT etc. which you can get here: https://zerodha.com/brokerage-calculator